The present invention relates to a method in which a tire component wound on a forming drum is bent back at both the side edges of the tire component around beads. The present invention also relates to an apparatus for that bending-back.
A conventional method of bending back a tire component and a conventional apparatus for that bending-back were disclosed in the Japanese Patent Application (OPI) No. 130834/87 (the term "OPI" as used herein means an "unexamined published application"). To bend back the tire component in the method or by the apparatus, the diameters of a pair of cylindrical bodies, whose diameters can be increased and decreased, are first decreased to a minimum value so that the beads of a tire to be manufactured are held by the cylindrical bodies. The beads are then set in prescribed positions on the tire component wound on a forming drum. After that, the diameters of the cylindrical bodies are increased to a maximum value and the bladders of the forming drum are inflated so that the tire component is pinch-held at both the side edges thereof by the bladders and the cylindrical bodies. The cylindrical bodies are then moved toward the longitudinally central portion of the forming drum as the tire component remains pinch-held at both the side edges thereof by the bladders and the cylindrical bodies, so that the tire component is bent back at both the side edges thereof around the beads by the cylindrical bodies, the bladders and the body of the forming drum. At that time, the maximum inside diameter of each of the cylindrical bodies needs to be equal to the sum of the outside diameter of the tire component and the double of the radial thickness of the space into which the bladder is pushed between the tire component and the cylindrical body as the bladder is inflated.
If the length of each bent-back portion of the tire component, which is equal to the distance from the position of the set bead to the nearby side edge of the tire component, is larger than the radial thickness of the space, the tire component can be securely pinch-held by the cylindrical bodies and the bladders to bend back the tire component at both the side edges thereof around the beads while keeping the bent-back portions of the tire component in strong pressure contact with the beads, to make the quality of the bending-back high. However, if the length of each bent-back portion of the tire component is smaller than the radial thickness of the space, the tire component cannot be securely pinch-held at both the side edges thereof by the cylindrical bodies and the bladders but the bent-back portion is likely to be simply pushed onto the bead by the bladder to make it impossible to always securely bend back the tire component at the side edges thereof to render the quality of the bending-back thereof good. This is a problem.